/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.mina.core.file;

import java.io.IOException;
import java.nio.channels.FileChannel;

/**
 * Manage a File to be sent to a remote host.
 * We keep a track on the current position, and the number of already written bytes.
 */
public final class DefaultFileRegion implements FileRegion {
	/** The channel used to manage the file */
	private final FileChannel channel;

	/** The original position in the file */
	private final long originalPosition;

	/** The position in teh file */
	private long position;

	/** The number of bytes remaining to write */
	private long remainingBytes;

	/**
	 * Creates a new DefaultFileRegion instance
	 *
	 * @param channel The channel mapped over the file
	 * @throws IOException If we had an IO error
	 */
	public DefaultFileRegion(FileChannel channel) throws IOException {
		this(channel, 0, channel.size());
	}

	/**
	 * Creates a new DefaultFileRegion instance
	 *
	 * @param channel The channel mapped over the file
	 * @param position The position in teh file
	 * @param remainingBytes The remaining bytes
	 */
	public DefaultFileRegion(FileChannel channel, long position, long remainingBytes) {
		if (channel == null)
			throw new IllegalArgumentException("channel can not be null");
		if (position < 0)
			throw new IllegalArgumentException("position may not be less than 0");
		if (remainingBytes < 0)
			throw new IllegalArgumentException("remainingBytes may not be less than 0");

		this.channel = channel;
		this.originalPosition = position;
		this.position = position;
		this.remainingBytes = remainingBytes;
	}

	@Override
	public long getWrittenBytes() {
		return position - originalPosition;
	}

	@Override
	public long getRemainingBytes() {
		return remainingBytes;
	}

	@Override
	public FileChannel getFileChannel() {
		return channel;
	}

	@Override
	public long getPosition() {
		return position;
	}

	@Override
	public void update(long value) {
		position += value;
		remainingBytes -= value;
	}
}
